Blade retainer



Nov. 18, 1969 F. D. BEAN 3,479,009

BLADE RETAINER Filed May 15, 1968 INVENTOR.

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ATTORN EY- United States Patent 3,479,009 BLADE RETAINER Fredrick D.Bean, Cincinnati, Ohio, assignor to General Electric Company, acorporation of New York Filed May 15, 1968, Ser. No. 729,153 Int. Cl.F01d /32 US. Cl. 416-216 4 Claims ABSTRACT OF THE DISCLOSURE A devicefor axially retaining a blade root within a slot formed in the peripheryof a supporting rotor disc and having a pair of strips joined at one endby an integrally formed loop or head. The strips are adapted to beinserted within a passage extending across the disc between the bladeroot and the bottom surface of the slot. After insertion into thepassage and with the loop abutting portions of one end of the disc andthe blade root, the projecting ends of the strips are formed intogenerally oppositely extending tabs which abut portions of the other endof the disc and blade root to thereby axially lock the blade within itsslot. The bottom surface of the blade root may be formed with a channelfor engaging the strips and preventing contact between the strips andthe slot side walls. The strips may be formed with means to yieldinglyurge the blade radially outwardly of the slot and into radial lockingabutment therewith.

This invention relates to blade locking means for retaining compressorblades, turbine blades and the like within the peripheral slots of asupporting rotor or disc.

In removal and replacement of turbomachinery rotor blades it isdesirable that the blade locking means or retainer used to axiallyretain each blade within its respective rotor slot be adapted to beremoved and replaced or reinserted without necessitating prior removalof the blade from the rotor slot. This is particularly important wherethe blades are formed with interlocking shrouds, each of which abuts andlocks with the shroud of the immediately preceding and succeeding bladeshroud. To remove one such interlocking shrouded blade from a fullyassembled rotor, it is necessary to first remove the blade locking meansor retainers for a sector of blades on either side of the blade to beremoved. The lossened blades are then successfully fanned out axiallyand radially until the blade to be removed can be slipped axially,unimpaired by adjacent shrouds, out of its rotor slot. It will be noted,then, that if the blades within each loosened sector must first beremoved from their rotor slots before they can be resecured, all bladeswould have to be removed in order to replace one blade. Accordingly, itis extremely desirable to provide blade locking means which can beremoved and replaced without removing the blades from their slots.

A primary object of this invention, therefore, is to provide an improvedretainer for axially securing a blade within a rotor or disc slot whichcan be removed and replaced without removing the blade from its slot.

Another object of this invention is to provide blade locking means asabove which overcomes the problem of loose assembly of parts due tospringback of bent tabs.

A further object of this invention is to provide blade locking meanswhich facilitates balancing of the rotor blade assembly.

Other objects and advantages of this invention will become apparent uponreading the following description of the preferred embodimen Brieflystated, in accordance with one embodiment of this invention, means areprovided to axially retain a blade within a slot formed in a supportingrotor disc in a manner which permits separate removal and replacement ofa single blade from a fully assembled rotor and includes a pair ofstrips extending from one side of the disc and blade root to the otherwithin a passage existing between the blade root and the slot bottom.The strips are suitably joined at one end, outwardly of the passage, bymeans which abut portions of one side of the disc and blade root. Theother ends of the strips are formed into generally radially oppositelyextending tabs, outwardly of the passage, which abut the other side ofthe disc and blade root and axially lock the blade within the slot.

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter of this invention, it isbelieved the invention will be better understood from the followingdescription of the preferred embodiment taken in connection with the accompanying drawing wherein:

FIGURE 1 is a partially exploded perspective view showing a portion ofan exemplary rotor blade assembly having one blade removed and employingthe blade locking means of this invention;

FIGURE 2 is an enlarged plan view of the exemplary rotor blade of FIGURE1;

FIGURE 3 is an enlarged cross-sectional view showing the blade lockingmeans of FIGURE 1; and

FIGURE 4 is a cross-sectional view taken along lines 4-4 of FIGURE 3.

Referring now to FIGURE 1, a portion of a rotatable disc or rotor hasbeen shown at 10 formed with a plurality of slots 12 at its peripherywhich extends from one side 14 of the disc 10 to the other side 16.Suitable turbine blades or buckets have been shown generally at 18 ashaving an airfoil portion 20, shroud means 22, a platform portion 24 anda root portion 26. The shroud means 22 have been shown in FIGURE 2 ascomprising a sector 28, usually arcuate and formed with generallyS-shaped inclined radial edges 30, each of which interlocks with theadjacent edge 30 of the preceding and succeeding shroud.

Each blade root 26 is formed with oppositely facing end surfaces 32 and34, a bottom surface 36 and substantially oppositely directed side wallsurfaces 38 and 40. As best seen in FIGURE 4, a channel 41, the functionof which will be hereinafter described, may be provided in the rootbottom surface 36 which extends from root end surface 32 to root endsurface 34.

Each disc slot 12 is formed with a base surface 42 and side walls 44 and46 and is sized in conjunction with the blade root 26 to enable theblade root portion to be slidably inserted into the slot in a generallyaxial direction relative to the rotational axis of the rotor. The slotside walls 44 and 46 and root side walls 38 and 40 are suitably shapedin a well known manner to abut and radially retain or lock each blade 18within its slot 12 against centrifugal forces generated when the disc 10rotates. Although a fir tree configured slot and root have been shown,it will be understood that other arrangements such as a dovetailconfiguration or the like may be employed. Additionally, as shown inFIGURE 4, the

blade root 26 and slot 12 are suitably sized so that when the root sidewalls 38, 40 are in radial locking abutmentwith slot side wall 44, 46, apassage 48 is formed between the root bottom surface 36 and the slotbase surface 42' which extends across the disc 10 from side 14 to 16.

The blade locking means for retaining each blade 18 axially within itsrespective slot 12 has been shown gen shown in FIGURE 4, to therebyprevent chafing between the strips and the side walls 44, 46. The strips52, 54 have a length greater than the length of the passage 48 so thatafter insertion into passage 48 and with the loop or head 56 abuttingsubstantially radially aligned portions of the disc side 14 and the rootend surface 32, sutficient material projects beyond the blade root endsurface 34 and the disc side 16 to enable tabs 58 and 60 to be formed.As best shown in FIGURE 3, the tabs 58 and 60 are formed generallynormal to the plane of their respective strips 52 and 54 and abut,respectively, generally radially aligned portions of the disc side 16and the blade root end surface 34, to thereby retain the blade againstaxial movement within its slot 12.

Accordingly, initial installation of the turbine blades or buckets 18 inthe rotatable disc may be readily ac; complished by slidably insertingeach blade root 26 into its respective slot 12, inserting the retainer50 of this invention into each passage 48 and forming the tabs 52 and54.

Normally, in forming the interlocking slot and blade root side walls 44,46 and 38, 40 respectively, sufficient clearance is left to enable theblade root to be easily slipped into the slot. This, of course, resultsin some radial play of the turbine blade 18 relative to the disc 10,which, in operation, is taken up by the action of centrifgual forcewhich urges each turbine blade or bucket radially outwardly and intoradial locking abutment with the slot side walls 44 and 46. However, tofacilitate balancing of a blade disc assembly, it is necessary that theblades be in the position they will assume during operation.Accordingly, each retainer 50 is preferably formed with means toyieldingly urge each blade 18 radially outwardly within its slot 12 andinto radial locking abutment with the slot side walls 44 and 46. To thisend, for example, and as shown in FIGURES 3 and 4, one strip 54 may beformed with a dimple or depression 62, intermediate the loop 56 and thetab 60, which is sized in depth to provide an overall radial thicknessto the strips 52, 54 slightly greater than the radial depth of passage48. Due to the elasticity of the metal of the dimple, the retainer canbe forced into place, thereby holding the blade radially tight in itsslot to facilitate handling and balancing of the assembled rotor disc.

Since the blade locking means or retainer 50 of this invention isinsertable within the passage 48, it is possible to remove and replaceone turbine blade 18 without removal of every blade on the disc 10.

In replacing shroud interlocked blades or buckets of the type showngenerally at 18 and previously described, it is first necessary toremove the blade locking means or retainer 50 for a sector of blades oneither side of the blade to be removed. The blades within such sectorsare then axially and radially fanned out until the interlocking shroudedges 30 are free, whereupon the blade is axally removed and replaced.The replaced blade and each loosened blade 18 may then be axiallyresecured by simply inserting a blade retainer within each passage 48and forming the tabs 58 and 60 are previously described.

The retainer 50 may be conveniently formed of one continuous metallicmember which is bent or folded back on itself to define the loop or head56 and strips 52, 54. Because of such one piece construction, assemblyand stocking problems are greatly reduced.

As will be understood by those skilled in the art, blade retainers whichrely on bent tabs may result in some degree of axial looseness due totab springback or the inherent resiliency of the tab material. This is,of course, undesirable and is overcome in the blade retainer 50 of thisinvention by providing the preformed head or loop 56 which, duringinstallation and forming of the tabs 58 and 60, may be axially andresiliently deformed so that after the tabs are formed they will betensioned or yieldingly urged to maintain their abutment with the bladeroot end 34 and the disc side 16 by the springback of the head or loop56.

The foregoing is a description of an illustrative embodiment of theinvention and it is applicants intention in the appended claims to coverall forms which fall within the scope of the invention.

I claim:

1. In a turbomachine including a rotatable disc member having a firstside surface and a second side surface and at least one root-receivingslot extending transversely of said disc member at its periphery, and ablade member having a root portion engaged in said slot, said rootportion having a first end surface and a second end surface, said slotand said root portion being shaped to abut and radially lock the blademember to said disc form a passage therebetween extending transverselyof.

said disc member, locking means for axially retaining said blade rootwithin said slot, said locking means comprising:

a pair of generally fiat strips axially positionable within saidpassage,

means joining said strips at one end thereof outwardly of said passage,said joining means comprising an integral extension of said stripsformed as a loop and adapted for locking abutment with generallyradially aligned portions of said disc first side surface and said rootfirst end surface,

the other ends of said strips projecting out of said passage andformable into oppositely extending tabs abutting generally radiallyaligned portions of said disc second side surface and said root secondend surface.

2. The structure of claim 1 further characterized in that said joiningmeans is resiliently deformable along the axis of said passage when saidtabs are formed, whereby after said tabs have been formed said joiningmeans is operative to yieldingly urge said tabs into locking abutmentwith said disc second side surface and said root second end surface andthereby prevent axial looseness of said blade due to tab springback.

3. The structure of claim 1 further characterized in that said lockingmeans further includes means to yieldingly urge said blade root radiallyoutwardly into radial locking abutment with said slot.

4. The structure of claim 3 further characterized in that said yieldingmeans comprise a dimple formed in at least one said strip intermediatesaid joining means and said tab, with said dimple having a depth sizedto provide an overall radial thickness to said strips greater than theradial depth of said passage.

References Cited UNITED STATES PATENTS 791,564 6/1905 Lynch. 2,297,77010/1942 Jcpson. 2,753,149 7/1956 Kurti.

2,786,648 3/ 1957 Ledwith. 2,971,744 2/1961 Szydlowski.

FOREIGN PATENTS 202,682 2/ 1955 Australia. 1,031,802 3/1953 France.

691,380 5/1953 Great Britain.

EVERETTE A. POWELL, JR., Primary Examiner

